Search Results (2)

This innovative study introduces an eco-conscious and cost-effective approach to synthesizing gelatin-based carbon dots (CDs) via two distinctive methods: hydrothermal processing in a muffle furnace (CDs-MF) and domestic microwave (CDs-MW). Both strategies harness natural, low-cost materials and prioritize simplicity, sustainability, and environmental friendliness, culminating in effective fluorescent sensing of the pesticide thiamethoxam (TMX). For the hydrothermal route, the investigation explores two purification approaches—ultracentrifugation (CDs-MF-C) and 0.22 µm syringe filtration (CDs-MF-F)—while the microwave-derived CDs (CDs-MW) undergo dialysis alone. This study aims to investigate how synthesis and purification impact the CDs structural, morphological, and photophysical characteristics. The difference in size was obtained from transmission electron microscopy (TEM): 30–40 nm for CDs-MF-C, 12–15 nm for CDs-MF-F, and 3–6 nm for CDs-MW. Fluorescence emission performance reveals that CDs-MF-F performs a fluorescence quantum yield of 27%, CDs-MF-C at 23%, and CDs-MW at a modest 3%. All variants exhibit TMX detection via fluorescence quenching through the inner filter effect (IFE). Analytically, CDs-MF-C stands out with the lowest detection limit (LOD = 0.396 ppm) and quantification limit (LOQ = 1.317 ppm), followed by CDs-MF-F (LOD = 0.475 ppm; LOQ = 1.585 ppm) and CDs-MW (LOD = 0.549 ppm; LOQ = 1.831 ppm). These findings emphasize the unique interplay between the synthesis pathway, purification strategy, and functional performance, demonstrating the critical importance of tuning structural properties for optimizing carbon-dot sensors. Full article

The widespread use of thiamethoxam has led to pesticide residues that have sparked global concerns regarding ecological and human health risks. A pressing requirement exists for a detection method that is both swift and sensitive. Herein, we introduced an innovative fluorescence biosensor constructed from alendronic acid (ADA)-modified upconversion nanoparticles (UCNPs) linked with magnetic nanoparticles (MNPs) via aptamer recognition for the detection of thiamethoxam. Through base pairing, thiamethoxam-specific aptamer-functionalized MNPs (apt-MNPs) were integrated with complementary DNA-functionalized UCNPs (cDNA-UCNPs) to create the MNPs@UCNPs fluorescence biosensor. Thiamethoxam specifically attached to apt-MNPs, leading to their separation from cDNA-UCNPs, which in turn led to a reduction in fluorescence intensity at 544 nm following separation by an external magnetic field. The change in fluorescence intensity (ΔI) was directly correlated with the concentration of thiamethoxam, enabling the quantitative analysis of the pesticide. With optimized detection parameters, the biosensor was capable of quantifying thiamethoxam within a concentration span of 0.4–102.4 ng·mL⁻¹, and it achieved a detection limit as minute as 0.08 ng·mL⁻¹. Moreover, leveraging the swift magnetic concentration properties of MNPs, the assay duration could be abbreviated to 25 min. The research exhibited a swift and precise sensing platform that yielded promising results in samples of cucumber, cabbage, and apple. Full article